Lopping/Pruning trees

Ok, Im being puzzled for some time now...Does Anyone know of a new concept in pruning/lopping trees these days? I was taught to always prune tree branches at an agngle to allow water runoff. Over the past years I notice more and more that both domestic and public trees large and small are being lopped/pruned with straight across cuts. I do know the pruning rules for different plants, but the above pruning habit I notice sometimes work and sometimes dont. So is it a matter of the lack of knowledge of the person doing the job or a new concept that I have not read about?

 

If pruning say roses or general shrubs then I cut cleanly at an angle (45%)

For trees a straight or very slightly angled cut but not totally flush with the trunk.

For hedge topping a flat straight cut.

I dont follow any particular rules but use judgment to make asethetic and healthy cuts.

One of my bugbears is the lack of tidying up after hedge trimmer shrub pruning, It takes seconds to tidy any torn ends with secauters.